ABSTRACT: The objective of this study was to see the incidence of
peripheral laterality in schizophrenics and depressed patients. A total
of 147 male subjects (29 schizophrenics, 38 depressed, 80 non-patient
controls) were asked to indicate their preferences for hand, foot, eye,
and ear on the Sidedness Bias Schedule. The correlations among the
laterality quotients (LQ) in all the three groups were positive and
highly significant except the foot-eye correlation in the non-patient
controls. The left and mixed-handed schizophrenics and depressed
subjects exhibited extreme left and mixed preference for foot, eye, and
ear, respectively. Hand and ear preferences emerged as the predictors of
schizophrenia and depression in the logistic regression analysis. The
findings indicate a possible relationship between psychopathology and
extreme left-mixed dominance.

KEY WORDS: Peripheral laterality; Schizophrenia; Depression

INTRODUCTION

Since Flor-Henry (1) advocated the relationship between
lateralization and psychopathology and Hicks and Barton (2) reported
left handedness in 28% of the people with serious mental disorders
lateralization has been studied in relation to different types of
psychosis (3,4). Studies have also indicated association between
depressive symptoms and schizophrenia (5,6,7). Such research gained
impetus after propositions of the GBG model (Geschwind-Behan-Galaburda
model) (8-11). This model suggests a causal association between prenatal
testosterone levels and an array of psycho-biological phenomena.

The relationship between peripheral indices of laterality,
especially handedness and schizophrenia (12,13) as well as depression
and lateralized cognitive functions (14,15) has been a subject of
interest for last couple of decade. Interestingly enough neither of the
two pathologies have yielded a conclusive association with
lateralization. Initial studies indicated an increased proportion of
left and mixed handedness among schizophrenic patients (16), but recent
research attests its link with mixed handedness (17,18) and not
left-handedness. Chapman and Chapman (19) reported common observation of
mixed handedness in individuals measuring high on psychosis-proneness
and schizotype, a finding that was further supported by Kim et al (20)
and Richardson (21). Although majority of the studies have attested an
elevated incidence of non-right/ left handedness in schizophrenia
(22,23). Few researchers have also reported elevated right handedness
(24,25) in the schizophrenic patients. A couple of studies have reported
no association (26) between them. Studies examining left-handedness in
schizophrenics have not yet yielded conclusive findings (27).

Similarly the observations pertaining to hand lateralization and
depression also seem to be divided. Several researchers have confirmed
the prevalence of left-handedness in those scoring high on measures of
depression (28,29,30) whereas some have reported just the opposite (3,
31); however, few studies did not find any association between the two
(32).

Handedness, footedness, eyedness and eardness are the peripheral
indicators of hemispheric lateralization. However, eyedness has been
questioned as a direct indicator of cerebral dominance (4,33) because of
crisscrossing of optic fibers; footedness seems a better indicator (34),
though both are least susceptible to environmental influences (13).

Though much emphasis has been given to handedness, few studies have
investigated footedness (34) and eyedness (4,33,35,36) too. Schiffman

et al. (13) have reported left or mixed footedness in schizophrenia.
Like handedness, studies investigating eyedness as one of the indicators
of laterality in schizophrenia have reported contrasting results.
Schiffman et al. (13) found left or mixed eye dominance in
schizophrenics whereas pure left eye dominance has been reported by
others (36). A few have even reported mixed eye dominance (4,33) as well
as null association (35).

In the case of depression, compared to the other indices of
laterality, eardness seems to have consensus. Most of the studies have
used either dichotic listening or visual hemifield tests. Although few
arguments have been raised questioning the inferences drawn from studies
using dichotic listening tests and visual half-field techniques,
researchers in the area of laterality agree to its usage because
preference (for eye and ear) correlates quite well with hemispheric
differences. Bruder and associates (29, 37) have reported left ear
(right hemisphere) advantage on non-verbal dichotic listening task. Few
more studies (38) have reported similar findings. However, depressed
patients show a right ear (left hemisphere) advantage on dichotic fused
word or syllable tests (29). These findings lack universal acceptance
(37,39). Adults with non-anxious major depression exhibited right ear
(left hemisphere) preference for dichotic fused words whereas those with
comorbid anxiety exhibited left ear (right hemisphere) advantage on
dichotic complex tones. To the best of our knowledge studies describing
footedness and eyedness in depression and eardness in schizophrenia are
very few (40).

Cultural evolution across the world has favoured right-handedness
(41). However, while complying with social sanctions forcing or
anticipating right preference in Oriental societies (such as India), the
influence of left and mixed handedness might not replicate the
observations made on Western samples. Either because of the social
sanctions, genetic pool, or developmental vulnerabilities, the hand
preference pattern, especially left-handedness, in Indians is different
as compared to the western population. However, very few studies have
been conducted on the Indian sample (18,25,40) to investigate the
lateralization pattern of those suffering from certain types of
psychopathology. In the absence of sufficient studies it becomes
essential to verify the nature of this pattern and its correlates.

Studies carried out on otherwise normal Indian sample have
attempted to explore lateral preferences (42,43), hand preference and
approval among major religious groups and hand clasping among endogamous
groups (44). The prevalence of left-handedness has always been low in
India. Singh et al. (43) have reported it as low as 3.2 percent. They
observed a significant sex difference between handedness and relative
hand skill with females exhibiting higher right hand preferences. This
has been corroborated by other researchers (42,44). These studies have
reported greater likelihood of left-handedness in men than the women.
The prevalence of left handedness in later studies shows a small
increase in the percentage of left-handers. For example, Mandal et al.
(45) has reported 6.78% left-handers.

Accepting the relationship between schizophrenia, depression and
anomalous dominance the present study attempted to reexamine the
contradictory findings on all the peripheral indices of laterality. Our
primary aim was to find out the incidence of peripheral laterality in
patients with schizophrenia and depression and to validate laterality as
a predictor of both disorders. It was hypothesized that schizophrenics
and depressed would show higher incidence of non-right handedness as
compared to the non-patient controls.

METHODOLOGY

Subjects: A total of 147 male subjects (29 schizophrenics, 38
depressed, 80 non-patient controls) participated in the study. The
patients selected for this study were undergoing treatment at the
Institute of Mental Health, Amritsar, India. None of them were
hospitalized at the time of data collection. Proper consent of the
patients/ attendants and the consulting psychiatrist were obtained
before conducting the study. The patient's group did not manifest
acute symptoms and were communicative. The patients were selected for
the study on the basis of their medical records and further diagnoses
were done by the consulting psychiatrists adhering to the DSM-IV-TR
diagnostic criteria for Schizophrenia and depressive disorder. Only
those patients were included in the study whose symptom severity was
rated within mild to moderate range by the treating psychiatrist. The
schizophrenic patients were chronic exhibiting first-rank symptoms
(thought disorder, inappropriate affect, delusions). The non-patient
controls were from the adjoining cities. Unlike the patient group
subjects in the NC group were selected from a pool of 342 subjects,
6.23% of which were left handed. They were drawn from the students and
staff of various hospitals and universities. Because of this it was
possible to strike some balance in terms of the number of subjects in
the three categories. The NC group (N 80) had 21.25% left-handers,
23.75% mixed-handers, and 55% right-handers. They had disclosed the
absence of any history of psychiatric treatment or hospitalization in
their disclosure form. However, this group was not screened for DSM
IV-TR criteria.

The mean age and education of NC group were 23.36 (SD 2.28) and
12.26 (SD 3.74), respectively. The mean age and education of
schizophrenic ([M.sub.age] = 23.14, SD 2.12; [M.sub.education] = 10.31,
SD 4.23) and depressed ([M.sub.age] = 23.52, SD 3.26; [M.sub.education]
= 11.42, SD 1.26) groups were also akin. The groups did not differ in
terms of age and education. All the subjects belonged to middle
socioeconomic class and conversed in Punjabi. They were also proficient
in Hindi. Both the languages are read from left to right.

Measures: The Sidedness Bias Schedule (45) was administered and
subjects were asked to indicate their preference for unimanual
activities on a 5-point scale (1= never, 5 = always). The subjects had
to indicate their preference for left as well as the right hand on the
37-item questionnaire (Hand: writing, eating, throwing a ball, lifting a
bucket full of water, using a spoon to stir, keying the lock, winding
the lock, using scissors, painting, threading the needles, combing,
brooming, screwing a nut, hammering a nail, opening the tap, switching
the light, lighting a matchstick, tooth brushing, sorting cards, using
knife, using racket for games, unscrewing the jar; Foot: kicking a ball,
foot extended to climb a bus, foot on which body weight rested in
standing posture, foot extended to ride a bicycle/vehicle, foot extended
in long jump; Eye: seeing through a telescope, snapping photograph by
camera, gun shooting, seeing through a keyhole, preferred eye to wink;
Ear: hearing telephone when both hands are free, hearing a pocket-radio,
matching musical tune, sensing tick movement in wrist watch, hearing a
low voice).

Several authors have developed questionnaires to measure hand
preference (46-49). Concurrent researchers use either of them. However,
as hand preference and performance have often turned uncorrelated for a
variety of perceptuo-motor tasks (50, 51) and cultural constraints play
key role in determining hand preference, we opted to use Sidedness Bias
Schedule developed by Mandal et al. (45). This schedule (test-retest
reliability r = 0.88) has been widely used in India (52,53,54). On the
basis of laterality quotient (LQ = right- left/right + left) subjects
were classified as right-handers (+. 50 to +1.00) and left-handers (-.50
to -1.00) considering it a continuous variable. Intermediate scorers
were classified as mixed-handers. The schedule also indicates bias (LQ)
for foot, ear and eye.

RESULTS

The mean of LQs for hand, foot, eye, and ear preferences of the
schizophrenic, depressed, and NC groups are given in table 1.

An interesting observation emerged out when cross tabulation was
performed to see foot, eye, and ear dominance with respect to
handedness. All the left -handed schizophrenics and depressed subjects
had left-preference for foot, eye, and ear as well. Similar trend was
seen in the mixed- handed schizophrenics and depressed subjects. All of
them demonstrated mixed-foot, eye, and ear preferences. Further, all the
right-handed schizophrenics showed right-eye preference but the foot
(23.07% mixed, 76.98% right) and ear preferences (46.15% mixed, 53.85%
right) were always non-left in nature. The right-handed depressed had
mixed (5.71%) as well as right (94.29%) footedness. However, their eye
and ear preferences were skewed in distribution. 2.86% of them had left,
20% mixed, and 77.14% had right eyedness. Similarly, 5.71% had left,
22.86% mixed, and 71.43% had right earedness. Unlike the patient groups,
the foot, eye, and ear scores of the right-handed normal controls were
distributed. The footedness scores of the mixed-handers were also spread
across the three categories (left, mixed, and right). However, they
exhibited mixed-eye and ear preferences only. All the left-hander had
left footedness and mixed-earedness. 94.12% of them had mixed and 5.88%
right-eyedness. This indicated a possible relationship between
psychopathology and extreme left-mixed dominance. Figure 1 illustrates
the spread of LQ scores of all the four indices and symptoms.

[FIGURE 1 OMITTED]

Further, Pearson correlations were computed. The correlations
between the LQs for hand, foot, ear, and eye are shown in Table 2 and 3.
The correlations among all the variables were positive and highly
significant when total LQ scores were taken into account. Similar
observations were obtained when correlation was computed separately for
the three groups except the foot-eye correlation (r = .13) in the NC
group which did not turn significant.

As the outcomes were categorical logistic regression was carried
out to assess the nature of relationship between LQ, schizophrenia, and
depression. At the first step attempt was made to differentiate between
normal controls and the patient groups (0 = patient groups, 1 = NC). The
obtained -2LL (143.228) and the goodness of fit (Hosmer & Lemeshow
[chi square] = 175.391, df = 8, p <.001) were indicative of a better
fit. The observed R square suggests that laterality quotient can predict
schizophrenia and depression to certain extent (Cox and Snell R square =
.332, Nagelkerke R square = .444). The laterality quotient of hand and
ear emerged as significant predictors of pathology (see table 3) with B
values indicating that schizophrenia and depressive disorder increases
with decrease in LQ for handedness and eardness. It is imperative that
decrease in LQ will result to increase in non-right hand and ear
preferences. Therefore it can be interpreted that left and mixed hand
and ear preferences are significant predictors of schizophrenia and
depression, thus accepting the hypothesis.

Thereafter logistic regression was performed to see if LQ of the
four indices can establish distinction between schizophrenics and
depressed (0 = schizophrenics, 1 = depressed). There was a significant
difference between foot preference of schizophrenics and depressed
subjects (see table 3); -2LL value was 81.985 with smaller Cox and Snell
[R.sup.2] (.135) and Nagelkerke [R.sup.2] (.181) values. Further, Hosmer
and Lemeshow [chi square] (11.567) did not turn significant

DISCUSSION

The present findings do not support high incidence of left
handedness in schizophrenic and depressed subjects in comparison to the
non-patient controls. The higher incidence of right handedness in
schizophrenics lends support to the findings of Taylor et al. (24) and
Tiwari (25). The present findings of depressed subjects are in
consonance with few earlier studies (3,31). It merits mention here that
the previous studies on Indian samples have come forward with
contrasting findings. While Tiwari (25) has reported right-hand
dominance in schizophrenics, Upadhyay et al. (18) reports
mixed-handedness in them. Present study supports the findings of Tiwari
(25).

The left and mixed-handed schizophrenics and depressed subjects
exhibited extreme left and mixed preference for foot, eye, and ear,
respectively. This finding is of substantive importance. According to
Kang and Harris (55) inconsistent left-handers show cross lateral
preference for foot, whereas consistent lefthanders show uncrossed
preference. These observations were made on normal subjects. The present
findings show an extreme side-bias in left and mixed-handed
schizophrenics and depressed subjects indicating a possible relationship
between schizophrenia, depression, and cerebral lateralization.

Studies of western societies have yielded 9:1 (right:left)
demographic ratio (56) with majority reporting a continuous J-shaped
distribution (57). However, the handedness distribution in male
right-handers reported by Tan (58) was not J-shaped. Further, McManus
(56) has also advocated that the number of left-handers have increased
from the last century. This distribution is visible in the schizophrenic
and depressed groups reported in this study but the NC group seems to
violate it. It merits mention that the NC group was selected from a pool
of subjects where 6.23% were left-handers. Although the distribution of
hand preference is not exactly J-shaped in the Indian society the
selection of mixed and right-handers for the present study has lead to
the higher incidence rate of left and mixed peripheral lateralities in
the NC group. It merits mention that social and parental pressure in the
Indian society demands switching hand preference in those who are
innately left-handed. However, we did not collect information about the
history of hand change in the subjects.

The correlations between the LQs for hand, foot, ear, and eye are
similar to those reported earlier (51,52). The nonsignificant
correlation between hand and eye in the normal controls stands in
isolation. Though Cannon et al. (4,33) has questioned eyedness as a
direct indicator of laterality several studies have reported modest
correlation between hand and eye. It merits mention that Hebbal and
Mysorekar (59) failed to find any interrelationship between them.

It is also interesting to note that footedness, eyedness, and
earedness are least susceptible to cultural influences. As crisscrossing
of optic fibers blur the possibility of eyedness as an indicator of
lateralization, the other two relatively influence-free measures (from
cultural sanctions) have emerged as the predictors of schizophrenia and
depression. Neurological investigations have endorsed certain
abnormalities in the brains of persons with schizophrenia are restricted
to or are worse usually in the left hemisphere. For example,
schizophrenia subjects show thinning of the left parahippocampal gyrus
and fusiform gyrus (60), left temporal horn enlargement (61), reduction
in size of the left medial temporal lobe (62), and loss of synaptic
proteins from the left thalamus (63). It merits mention that few
investigators have come forth with neurobiological evidence signifying
association between schizophrenia and reduced corticocortical
(64)/fronto-temporal connectivity (65). As the present study did not
investigate the role of any such variable, it is not possible for us to
lend support to the neurobiological observations simply on the basis of
behavioural variables.

The present study has certain limitations also. It had only male
sample. Hand preferences were not looked to separate out skilled and
unskilled activities. Further studies on diverse and larger samples are
needed beside the study of female population to avoid sample-specific
characteristics obtained in the present study

(63.) Landen M, Davidsson P, Gottfries CG, et al. Reduction of the
small synaptic vesicle protein synaptophysin but not the large dense
core chromogranins in the left thalamus of subjects with schizophrenia.
Biol Psychiatry. 1999 Dec;46(12):1698-702.